fn:substring-before

Returns that part of the given input string that occurs before the first occurrence of the string given in $arg2.

substring-before($arg1 as xs:string?, $arg2 as xs:string?) ➔ xs:string

Arguments
	$arg1	xs:string?	The input string
	$arg2	xs:string?	A substring of the input string; the function returns the part of the input string before this substring
Result		xs:string

substring-before($arg1 as xs:string?, $arg2 as xs:string?, $collation as xs:string) ➔ xs:string

Arguments
	$arg1	xs:string?	The input string
	$arg2	xs:string?	A substring of the input string; the function returns the part of the input string before this substring
	$collation	xs:string	The collation to be used for comparing characters
Result		xs:string

http://www.w3.org/2005/xpath-functions